The invention relates to a gas-porous plug for metallurgical vessels comprising a refractory moulding in which at least one gas passage duct is provided in the form of an interstice running through the plug from a cold side of the plug to a hot side thereof.
Gas-porous plugs of this type are referred to as so-called interstitial flushing devices and function to blow reaction or purification gases into molten metal or metal melts.
In the latter context, such gas-porous plugs are usually used in the base area of a refractory lining of a metallurgical vessel, particularly a steel ladle, and such metallurgical vessels are pressurized with compressed gas through a gas feed pipe.
Conventional gas-porous plugs are known which are constituted as an inner conically shaped refractory moulding or body over which a second outer conically shaped moulding is positioned. In order to define a gap between the inner and outer mouldings, strip-shaped spacers are inserted in the gap or interstices therebetween. Thus, such gas-porous plugs are not monolithic structures.
A peripheral side wall and a base area of such conventional gas porous plugs are also usually provided with a gas-tight, welded sheet metal casing having a base positioned at a distance from the underside or cold side of the gas-porous plug to create a gas feed chamber. A gas feed pipe is welded to the metal base and opens into the latter gas feed chamber.
In another conventional gas-porous plug, the interstice is formed between the side of the sheet metal casing and the refractory moulding. However, such gas-porous plugs are no longer used owing to their relatively low wear resistance.
Another gas-porous plug of a conventional construction is disclosed in DE-OS 43 12 988 in which gas passage ducts are defined as a three-dimensional network in the interior of a monolithically cast refractory moulding utilizing a conventional tensioning device. However, the manufacture of this gas-porous plug is relatively complicated and the inner gas passage ducts are also relatively long which results in comparative high pressure gas losses when in use.
In another conventional gas-porous plug disclosed in DE-OS 38 23 897, threads or strips are inserted into a casting mould utilizing a tensioning device which is pulled or burnt out after the moulding has set. This moulding is also manufactured as a monolithic structure but the tensioning of the individual threads constitutes a relatively complicated manufacturing process.